Seat supporting structure in saddle riding type vehicle

ABSTRACT

Engaging pieces ( 35 ) for receiving a load are provided in sections of a rear frame ( 26 ) corresponding to both ends of a seat ( 9 ) in a width direction of a vehicle so as to project upward. Movably supported plates ( 61 ), which are movably supported by the engaging pieces ( 35 ), are formed at both ends of a bottom plate ( 51 ) of the seat ( 9 ) in the width direction of the vehicle, which are sections opposed to the engaging pieces ( 35 ). These movably supported plates  61  are positioned above the other sections of the bottom plate ( 51 ). Inner cushion materials ( 53, 54 ) harder than a cushion material ( 52 ) on a seat surface side are provided between these movably supported plates ( 61 ). The bottom plate ( 51 ) of the seat ( 9 ) is movably supported by the projecting pieces ( 35 ) at both the ends thereof and is never displaced in a height direction. When a weight of a rider is applied to the seat ( 9 ) as an impact load, a section between both the ends is elastically deformed to curve downward viewed from a front-rear direction of the vehicle, and an amount of downward deformation of the bottom plate ( 51 ) can be reduced. When the rider is seated, the rider sits on the inner cushion materials ( 53, 54 ) via the cushion material ( 52 ) on a seat surface side, and an impact, which cannot be eased by the cushion material ( 52 ) on the seat surface side, is eased by the inner cushion materials ( 53, 54 ).

TECHNICAL FIELD

The present invention relates to a seat supporting structure in a saddleriding type vehicle in which both ends in a vehicle width direction of aseat are movably supported by a rear flame of a body frame.

BACKGROUND ART

Conventionally, a seat of a motorcycle, which is an example of a saddleriding type vehicle, adopts a structure in which a cushion materialconsisting of urethane foam or the like is placed on a bottom plate ofplastics and the cushion material is covered with a skin. In order tofix this seat to a body frame of the motorcycle, a front end of thebottom plate in a front-rear direction (longitudinal direction) of thevehicle is engaged with the rear of a fuel tank and the rear end of thebottom plate is fastened by bolts. In addition, in the center of theseat in the front-rear direction of the vehicle, a leg, which isintegrally formed to protrude downward from the bottom plate, is movablysupported by the rear frame, such that the body frame can support aweight of a rider.

On the other hand, as a motorcycle, there is a so-called motocrosser forcompeting for speed of running off-roads. A two-cycle engine is oftenused in this type of motorcycle in order to reduce a weight of thevehicle. In the motocrosser mounted with the two-cycle engine, a kicktype starter is used and a starter motor is not used.

The inventors consider mounting a four-cycle engine on the motocrosserand equipping the motocrosser with the starter motor.

Here, in equipping the motocrosser with the starter motor, it ispreferable to mount a battery for supplying power to the starter motorbelow a seat. However, this causes a problem in that a bottom plate ofthe seat hits the battery when the seat bends downward largely.

The bottom plate of the seat bends largely, for example, when thevehicle jumps and makes landing and a weight of a rider is applied tothe seat as an impact load. In other words, a large load is applied tothe seat, whereby a leg protrudingly provided on the bottom plateinclines to topple to the inside of the vehicle, and the center of thebottom plate in a width direction of the vehicle curves downward viewedfrom the front-rear direction. Thus, the bottom plate bends downwardlargely.

Note that, since the battery is a heavy object, a mounting position ofthe battery is restricted in bringing a center of gravity of the vehicleclose to an ideal position. For example, it is difficult to mount thebattery in a section other than a section below the seat, and it is noteasy to mount the battery in a lower position because it is likely thatthe battery interferes with other components located below the seat.

The deficiency can be eliminated if a position of the seat is set highor the bottom plate is formed of metal, for example, such that the seatdoes not bend easily. However, if the seat is set in a higher position,a seating position of a rider becomes higher and a center of gravity ata time of riding becomes higher. The rider is given a sense ofincongruity if the seat does not bend at all. In addition, thedeficiency can be eliminated if the seat is formed to be reduced inthickness so as to separate the bottom plate upward from the battery.However, when this structure is adopted, since a cushion material isreduced in thickness, the rider is given a feeling unpleasant as ifbuttocks of the rider hit the bottom plate via the cushion material whenthe rider is seated.

DISCLOSURE OF THE INVENTION

The invention has been devised in view of the circumstances describedabove, and it is an object of the invention to provide a seat supportingstructure in a saddle type vehicle with which a seat bends less easilywhile comfort in seating is prevented from being deteriorated.

The seat supporting structure in a saddle type vehicle according to theinvention is a seat supporting structure in which projecting pieces forreceiving a load are provided in sections of a rear frame, whichcorrespond to both ends of a seat in a width direction of a vehicle, soas to project upward, at both ends of a bottom plate of the seat in thewidth direction of the vehicle, which are sections opposed to theprojecting pieces, movably supported plates, which are positioned abovethe other sections of the bottom plate and movably supported by theprojecting pieces, are formed, and inner cushion materials harder than acushion material on a seat surface side are provided between thesemovably supported plates.

According to the invention, the bottom plate of the seat is movablysupported by the projecting pieces at both the ends thereof and is neverdisplaced in a height direction. When a weight of a rider is applied tothe seat as an impact load, a section between both the ends iselastically deformed to curve downward viewed from a front-reardirection of the vehicle. Therefore, although in the conventional seatsupporting structure, the leg provided in the bottom plate is movablysupported by the rear frame and the leg inclines due to the impact load,whereby the bottom plate itself is lowered, this does not occuraccording to the invention, and an amount of downward deformation of thebottom plate can be reduced.

In addition, for example, when the rider is seated to apply an impactload to the seat, the rider sits on the inner cushion materials via thecushion material on a seat surface side, and an impact, which cannot beeased by the cushion material on the seat surface side, is eased by theinner cushion materials. Consequently, despite the fact that the amountof deformation of the bottom plate of the seat is reduced and it becomesdifficult to ease the impact with elasticity of the bottom plate, therider is not given a feeling unpleasant as if the rider hits the bottomplate of the seat when the rider is seated. Moreover, riding comfort isnot damaged even if the seat is formed to have reduced thickness.

Therefore, since it is possible to form the seat so as to bend lesseasily and have reduced thickness while preventing seating comfort frombeing deteriorated, components such as a battery can be arranged in thevicinity below the seat without bringing the components and the seatinto contact with each other.

In the invention, it is also possible that engaging pawls projectingtoward the rear of the vehicle are provided at upper ends of theprojecting pieces, and engaging pieces, which face lower parts of theengaging pawls and engage with the engaging pawls, are provided in thebottom plate of the seat.

According to the structure, when a force of pulling seat sides upward isapplied to the seat sides by legs of the rider during running, it ispossible to receive this force with the rear frame via engaging parts ofthe engaging pawls and the engaging pieces.

Consequently, since the seat can be fixed to the rear frame firmly, itis possible to form the seat so as to have further reduced thickness andto form a large space below the seat.

In the invention, it is possible that the inner cushion materials areformed by stacking plural cushion materials different in hardness one ontop of another in layers such that those closer to the bottom plate arerelatively harder.

According to the structure, when an impact given to the seat by therider sitting on the seat is relatively small, a larger amount of impactis damped by the cushion materials closer to the seat surface, and whenthe impact is relatively large, the impact is also damped by the cushionmaterials closer to the bottom plate of the seat. Consequently, since adamping force is generated in the seat so as to correspond to amagnitude of a force applied by the rider when he sits on the seat, itis possible to provide stable seating comfort.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a motorcycle that adopts a seat supportingstructure according to the invention.

FIG. 2 is a side view showing a seat section in enlargement.

FIG. 3 is a side view of a rear frame.

FIG. 4 is a plan view of the rear frame.

FIG. 5 is a perspective view showing a state in which an air cleaner boxand a battery are attached to the rear frame.

FIG. 6 is a plan view of the rear frame.

FIG. 7 is a side view of the rear frame.

FIG. 8 is a view showing a seat, and FIG. 8(a) is a vertical sectionalview of a front side part of the seat and FIG. 8(b) is a side view of arear side part of the seat, the figures being drawn with a part, whereengaging pieces are formed, cut away.

FIG. 9 is a bottom view of the seat, and FIG. 9(a) shows a front of theseat and FIG. 9(b) shows a rear of the seat.

FIG. 10 is a sectional view along line X-X of the seat in FIG. 2.

FIG. 11 is a sectional view along line XI-XI of the seat in FIG. 2.

FIG. 12 is a sectional view along line XII-XII in FIG. 2.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be explained in accordance with the attached drawingsin order to describe the invention more in detail.

In the figures, reference numeral 1 denotes a motorcycle that is anexample of a saddle riding type vehicle, and the left and right in thefollowing description refers to a width direction of a vehicle whenfacing the front of the vehicle.

The motorcycle 1 is a so-called motocrosser and is mounted with awater-cooled four-cycle engine 2. The motorcycle 1 runs by driving arear wheel 3 with this engine 2. In FIG. 1, reference numeral 4 denotesa body frame of a cradle type; 5, a front wheel; 6, a front fork; 7, asteering handlebar; 8, a fuel tank; 9, a seat; 10, a cowling; 11, a sidecover; and 12, a muffler.

In the engine 2, an exhaust pipe 14 is connected to a front part of acylinder 13 in a front-rear direction (longitudinal direction) of thevehicle, and an intake system including a carburetor 15 and an aircleaner 16 is connected to a rear part of the cylinder 13. In addition,a crank case 17 of this engine 2 is equipped with a starter motor 18. Asshown in FIGS. 3 to 5, electric power is supplied to this starter motorfrom a battery 19 disposed below the seat 9.

As is well known conventionally, the body frame 4 is formed by a headpipe (not shown) that pivotably supports the front fork 6, a main pipe21 (see FIG. 4) that extends downward to the rear from an upper part ofthis head pipe above the engine 2, a pair of left and right seat pillartubes 22 that are connected to a rear end of this main pipe 21, a pairof left and right down tubes 23 (see FIG. 1) that extend downward to therear from a lower part of the head pipe, a rear arm bracket 24 thatconnects rear ends of this down tubes 23 and lower ends of the seatpillar tubes 22, and the like.

As shown in FIGS. 2 and 4, a rear frame 26 is attached to the rear endof the main pipe 21 via a bracket 25. In addition, a rear arm for rearwheel support 28 is swingably supported by the rear arm bracket 24 via apivot shaft 27.

As shown in FIGS. 2, 3, 6, and 7, the rear frame 26 includes a pair ofleft and right seat rails 31 that extend upward to the rear from thebracket 25 and back stays 32 that connect rear ends of the seat rails 31and the lower ends of the seat pillar tubes 22. The seat rails 31 andthe back stays 32 are formed of a pipe of aluminum alloy having a squareshape in section, respectively.

As shown in FIGS. 6 and 7, tabular brackets 34 for supporting a relayfor starter motor 33 and a front upper part of the air cleaner 16 arewelded to front ends of the seat rails 31 so as to extend to the innerside of the vehicle. In addition, locking pieces 35 for receiving a loadof the seat 9 to be described later are welded to the seat rails 31 in amiddle part in the front-rear direction of the vehicle. Projectingpieces according to the invention include the locking pieces 35. Asshown in FIG. 7, the locking pieces 35 are formed by vertical plates 36extending upward from upper surfaces of the seat rails 31 and pressurereceiving plates 37 extending from upper ends of these vertical plates36 to the inner side of the vehicle and to the rear of the vehicle.Locking pawls according to an invention of claim 2 include rear ends 37a projecting backward from the vertical plates 36 in these pressurereceiving plates 37. In addition, brackets 38 for fixing the rear end ofthe seat 9 are welded to the rear ends of the seat rails 31 in such amanner that the brackets 38 project upward.

As shown in FIGS. 3 and 4, the relay for start mortar 33 is surroundedby a cover for relay 39 in four sides excluding an upper side and a rearside. This cover 39 is supported by the tabular brackets 34 togetherwith the relay 33 and is formed such that, even when fuel flows down arear wall of the fuel tank 8 when the fuel is filled, it is possible toprevent the fuel from adhering to the relay for starter motor 33.

The air cleaner 16 includes an air cleaner box 40 that is housed in aspace formed between the seat rails 31 and the back stays 32 of the rearframe 26, an air cleaner element 41 that is provided inside this aircleaner box 40, and an air inlet duct 42 that connects the air cleanerbox 40 to the carburetor 16.

The air cleaner box 40 is formed in a box shape by combining pluralmembers, and an upper end thereof is fixed to the brackets 34 in a statein which a lower part thereof is supported by the backstays 32. On theupper end wall, among the plural members forming this air cleaner box40, a box for battery support 43 and a duct for air intake 44 are formedintegrally and arranged in the front-rear direction of the vehicle so asto recess the wall downward partially. An air intake of the duct for airintake 44 is denoted by reference sign 44 a in FIG. 4. In addition, anopening for maintenance 40 a (see FIGS. 3 and 5) is formed on a leftwall of the air cleaner box 40. This opening for maintenance 40 a is anopening for replacing and cleaning the air cleaner element 41 and isopened and closed by a cover denoted by reference numeral 45 in FIG. 2.

The box for battery support 43 is formed in a box shape opened upward,and the battery 19 is housed therein. In addition, a band 46 (see FIG.4) for pressing the battery 19 from above is attached to an upper end ofthis box for battery support 43. The duct for air intake 44 is disposedon a back side of the box for battery support 43 and communicates with aspace formed between the air cleaner box 40 and the seat 9 and theinside of the air cleaner box 40.

In FIGS. 3 and 5, a reservoir tank 47 for engine cooling water isattached to the rear end of the rear frame 26. Reference numeral 48denotes a mud guard and 49 denotes a rear fender formed integrally withthe mud guard 48.

As shown in FIG. 8(a), the seat 9 includes a bottom plate 51 that isformed in a predetermined shape with plastics, three kinds of cushionmaterials 52 to 54 to be described later that are provided on thisbottom plate 51, and a skin 55 that covers these cushion materials 52 to54. In addition, as shown in FIG. 2, this seat 9 is formed so as toextend along the front-rear direction of the vehicle from a rear upperpart of the fuel tank 8 to the rear fender 49 in the rear part of thevehicle. The front end of the seat 9 is supported by the fuel tank 8 andthe center and the rear end thereof in the front-rear direction issupported by the rear frame 26.

As is well known conventionally, a connection part of the front end ofthis seat 9 and the fuel tank 8 adopts a structure in which an engagingprojection 58 (see FIG. 2) of a T shape in section of the fuel tank 8 isinserted into an engaging hole 57 (see FIGS. 8(a) and 9(a)), which isformed in the center of the bottom plate 51 in the width direction ofthe vehicle, and engaged with the engaging hole 57. In addition, aconnection part of the center of the seat 9 in the front-rear directionof the vehicle and the rear frame 26 adopts a structure in which movablysupported plates 61 (see FIG. 10) integrally formed at both the ends inthe width direction of the bottom plate 51 comes into abutment againstthe upper end face of the locking pieces 35 and are movably supported bythe locking pieces 35.

As shown in FIGS. 10 and 11, the movably supported plates 61 are formedsuch that a rear portion from substantially the center in the front-reardirection at both the ends of the bottom plate 51 in the width directionof the vehicle is partially deviated upward. Note that a sectional shapeof a portion of the bottom plate 51 further a head of the front ends 61a of the movably supported plates 61 (see FIG. 9(a)) is formed in a Cshape opened downward. In addition, as shown in FIGS. 2, 8(b), and 10,engaging pieces 62, which project to the outside of the vehicle, areformed on vertical walls extending downward from the ends on the vehicleinner side of the movably supported plates 61, in other words, onvertical walls 51 b that connect a flat portion 51 a extending in thefront-rear direction and the movably supported plates 61 in the centerof the bottom plate 51 in the width direction of the vehicle.

The engaging pieces 62 are formed by extending portions 62 a that extenddownward from the movably supported plates 61 and the other extendingportions 62 b that extend forward from the lower end of this extendingportion 62 a. In a state in which the seat 9 is mounted on the vehicle,the other extending portions 62 b are located below the rear ends 37 a(engaging pawls) of the pressure receiving plates 37 provided in theengaging pieces 35, and the pressure receiving plates 37 are nipped bythe other extending portions 62 b and the movably supported plates 61.

As shown in FIG. 12, a connection part of the rear end of the seat 9 andthe rear frame 26 adopts a structure in which a supporting plate 63fixed to the bottom plate 51 is fixed by the bracket 38 at the rear endsof the seat rails 31 by a fixing bolt 64. In addition, a rear end of theside cover 11 is also fastened to this connection part by the fixingbolt 64.

A cushion material of the seat 9 includes the cushion material 52 on theseat surface side, which is provided in an entire area of a formationrange of the seat 9 and covered by the skin 55, and the inner cushionmaterials 53 and 54, which are provided to be stacked one on another onthe flat portion 51 a of the bottom plate 51 so as to be located betweenthe pair of left and right movably supported plates 61.

The cushion material 52 on the seat surface side is formed of a materialequivalent to that used in the conventional seat. As an example of thematerial forming the cushion material 52 on the seat surface side, thereis urethane foam. The cushion material 52 on the seat surface sideaccording to this embodiment is formed so as to be smaller in thicknessthan the conventional cushion material because the inner cushionmaterials 53 and 54 are provided as described later.

The inner cushion materials 53 and 54 are stacked one on another so asto form a tabular shape in layers. The inner cushion material 53 on theupper side is disposed on the inner cushion material 54 on the lowerside. In addition, these inner cushion materials 53 and 54 are formed ofmaterials harder than the cushion material 52 on the seat surface side,that is, each having a larger damping force against impact. To describemore in detail, the inner cushion materials 53 and 54 according to thisembodiment are formed of materials harder than the cushion material 52on the seat surface side and softer than the bottom plate 51 such thatthe inner cushion material 54 on the lower side is relatively harderthan the inner cushion material 53 on the upper side. As a materialforming the inner cushion materials 53 and 54, micro-cell urethane foam(product name: polon) is used in this embodiment. In order to changehardness, a density of air holes formed in the inside at the time offormation is changed.

In order to attach the seat 9 constituted as described above to the rearframe 26, first, the engaging projection 58 of the fuel tank 8 isinserted into the engaging hole 57 of the bottom plate 51, the movablysupported plates 61 of the bottom plate 51 are movably supported by theengaging pieces 35 of the rear frame 26, and the seat 9 is translatedforward. By moving the seat 9 in this way, the engaging projection 58engages with the engaging hole 57 and, at the same time, the pressurereceiving plates 37 of the locking pieces 35 engage with the engagingpieces 62 of the bottom plate 51. Thereafter, the supporting plate 63 atthe rear end of the seat 9 is fixed to the bracket 38 at the rear endsof the seat rails 31 by the fixing bolt 64, whereby attachment work ofthe seat 9 ends.

According to the supporting structure for the seat 9, the bottom plate51 of the seat 9 is never displaced in a height direction because boththe ends of the bottom plate 51 in the width direction of the vehicleare movably supported by the engaging pieces 35 of the rear frame 26.Thus, even in the case in which a weight of a rider is applied to theseat 9 as an impact load, a portion between both the ends is simplydeformed elastically to curve downward viewed from the front-reardirection of the vehicle.

Consequently, whereas, in the conventional seat supporting structure,the leg provided in the bottom plate of the seat is movably supported bythe rear frame and inclines due to the impact load, whereby the bottomplate itself is lowered, according to the above-mentioned structure,this does not occur, and an amount of downward deformation of the bottomplate 51 can be reduced.

In addition, since the inner cushion materials 53 and 54 harder than thecushion material 52 on the seat surface side are provided in the seat 9,for example, when the rider is seated to apply an impact load to theseat 9, the rider sits on the inner cushion materials 53 and 54 via thecushion material 52 on the seat surface side, and an impact, whichcannot be eased by the cushion material 52 on the seat surface side, iseased by the inner cushion materials 53 and 54. Consequently, despitethe fact that the amount of deformation of the bottom plate 51 of theseat 9 is reduced and it becomes difficult to ease the impact withelasticity of the bottom plate 51, the rider is not given a feelingunpleasant as if the rider hits the bottom plate 51 of the seat 9 whenthe rider is seated. Moreover, riding comfort is not damaged even if theseat 9 is formed to have reduced thickness.

As a result, the seat 9 can be formed so as to bend less easily and havereduced thickness, and the battery 19 can be mounted in the vicinitybelow the seat 19 in a state in which the battery 19 is not brought intocontact with the bottom plate 51.

Moreover, according to the seat supporting structure described above,the pressure receiving plates 37, which project backward from the upperends of the engaging pieces 35 of the rear frame 26, are provided, andthe engaging pieces 62, which face the lower part of this pressurereceiving plate 37 and engage with these pressure receiving plates 37,are provided in the bottom plate 51 of the seat 9. Thus, when a force ofpulling the sides of the seat 9 upward is applied to the sides of theseat 9 by legs of the rider during running, this force is transmitted tothe rear frame 26 via the engaging parts of the pressure receivingplates 37 and the engaging pieces 62. In other words, it is possible tofix the seat 9 firmly to the rear frame 26.

In addition, the inner cushion materials 53 and 54 are formed bystacking plural cushion materials different in hardness one on anotherin layers such that the inner cushion material 54 on the lower sidecloser to the bottom plate 51 is relatively harder than the innercushion material 53 on the upper side. Thus, when an impact applied bythe rider to the seat when he sits on the seat 9 is relatively small, alarger amount of impact is damped by the cushion material closer to thesurface of the seat 9, and when the impact is relatively large, theimpact is also damped by the cushion material closer to the bottom plate51 of the seat 1. Consequently, it is possible to generate a dampingforce in the seat 9 so as to correspond to a magnitude of a forceapplied by the rider when he sits on the seat 9.

In the embodiment described above, the example in which the innercushion material includes the inner cushion material 53 on the upperside and the inner cushion material 54 on the lower side is described.However, the inner cushion material may be one, or three or more innercushion materials can also be used. In addition, the vehicle may be amotor three wheel or four wheel car.

1. A seat supporting structure in a saddle riding type vehicle,comprising: projecting pieces for receiving a load are provided insections corresponding to both ends of a seat in a rear frame so as toproject upward; a bottom-plate of the seat includes: a flat portion thatconstitutes a center of the bottom plate in a width direction of avehicle and extends in a front-rear direction; movably supported platesthat are formed at both ends of the bottom plate in the width directionof the vehicle, which are sections opposed to the projecting pieces,positioned above the flat portion and movably supported by theprojecting pieces; and vertical walls that connect ends of the flatportion in the width direction of the vehicle and ends on inner sides ofthe vehicle of the movably supported plates, and inner cushion materialsharder than a cushion material on a seat surface side are provided onthe flat portion so as to be located between both the movably supportedplates and between both the vertical walls.
 2. The seat supportingstructure in a saddle riding type vehicle according to claim 1, whereinengaging pawls projecting to a rear of the vehicle are provided at upperends of the projecting pieces and engaging pieces, which face a lowerpart of the engaging pawls and engage with the engaging pawls, areprovided in the bottom plate of the seat.
 3. The seat supportingstructure in a saddle riding type vehicle according to claim 1, whereinthe inner cushion materials are formed by putting cushion materialsdifferent in hardness one on another in layers such that the cushionmaterials closer to the bottom plate are harder.
 4. The seat supportingstructure in a saddle riding type vehicle according to claim 1, whereinthe seat extends in the front-rear direction of the vehicle.
 5. The seatsupporting structure in a saddle riding type vehicle according to claim1, wherein both ends of the seat in the width direction of the vehicleare movably supported by the rear frame.
 6. The seat supportingstructure in a saddle riding type vehicle according to claim 1, whereinthe rear frame is connected to a main pipe via a bracket.
 7. The seatsupporting structure in a saddle riding type vehicle according to claim1, wherein the rear frame includes a pair of left and right seat rails.8. The seat supporting structure in a saddle riding type vehicleaccording to claim 7, wherein the projecting pieces are welded to theseat rails.
 9. The seat supporting structure in a saddle riding typevehicle according to claim 1, wherein the bottom plate is made ofplastic.
 10. The seat supporting structure in a saddle riding typevehicle according to claim 1, wherein a skin material covers the cushionmaterials.
 11. A seat supporting structure in a saddle riding typevehicle, comprising: means for receiving a load are provided in sectionscorresponding to both ends of a seat in a rear frame so as to projectupward; a bottom-plate of the seat includes: a flat portion thatconstitutes a center of the bottom plate in a width direction of avehicle and extends in a front-rear direction; movably supported platesthat are formed at both ends of the bottom plate in the width directionof the vehicle, which are sections opposed to the means for receiving,positioned above the flat portion and movably supported by the means forreceiving; and vertical walls that connect ends of the flat portion inthe width direction of the vehicle and ends on inner sides of thevehicle of the movably supported plates; and inner cushion materialsharder than a cushion material on a seat surface side are provided onthe flat portion so as to be located between both the movably supportedplates and between both the vertical walls.
 12. The seat supportingstructure in a saddle riding type vehicle according to claim 11, whereinengaging pawls projecting to a rear of the vehicle are provided at upperends of the means for receiving and engaging pieces, which face a lowerpart of the engaging pawls and engage with the engaging pawls, areprovided in the bottom plate of the seat.
 13. The seat supportingstructure in a saddle riding type vehicle according to claim 11, whereinthe inner cushion materials are formed by putting cushion materialsdifferent in hardness one on another in layers such that the cushionmaterials closer to the bottom plate are harder.
 14. The seat supportingstructure in a saddle riding type vehicle according to claim 11, whereinthe seat extends in the front-rear direction of the vehicle.
 15. Theseat supporting structure in a saddle riding type vehicle according toclaim 11, wherein both ends of the seat in the width direction of thevehicle are movably supported by the rear frame.
 16. The seat supportingstructure in a saddle riding type vehicle according to claim 11, whereinthe rear frame is connected to a main pipe via a bracket.
 17. The seatsupporting structure in a saddle riding type vehicle according to claim11, wherein the rear frame includes a pair of left and right seat rails.18. The seat supporting structure in a saddle riding type vehicleaccording to claim 17, wherein the means for receiving are welded to theseat rails.
 19. The seat supporting structure in a saddle riding typevehicle according to claim 11, wherein the bottom plate is made ofplastic.
 20. A method for manufacturing a seat supporting structure in asaddle riding type vehicle, comprising: receiving a load by projectingpieces provided in sections corresponding to both ends of a seat in arear frame so as to project upward; providing a bottom-plate of the seathaving a flat portion that constitutes a center of the bottom plate in awidth direction of a vehicle and extends in a front-rear direction;forming movably supported plates at both ends of the bottom plate in thewidth direction of the vehicle, which are sections opposed to theprojecting pieces, positioned above the flat portion and movablysupported by the projecting pieces; connecting ends of the flat portionin the width direction of the vehicle and ends on inner sides of thevehicle of the movably supported plates with vertical walls; andproviding inner cushion materials harder than a cushion material on aseat surface side on the flat portion so as to be located between boththe movably supported plates and between both the vertical walls.